The snowman mobs spawn on the surface of the world. They are hostile, so they won't spawn with peaceful mode on.

1.Junk-Jack-Wiki2. The world is big, 256 blocks high and 768 across.3. Who is John Galt?4. Lack of objection does not indicate consent.5. We scream, we shout, we wail, we cry; but in the end we all must die.